Electric heating system



June 28, 1949. w. G. GRABEAU ELECTRIC HEATING SYSTEM Filed May l5, 1946 2 Sheets-Sheet 1 INVENTOR.

FIG.6

Patented June 28, 1949 'UNITED-f PATENT ermee ELECTRIC AHEATING SYSTEM Walter 'G'. Graheau, West Roxbury, Mass.

Application May`15, 1946, SeriaifNo..669,'7-75 (Cl. 21S-391) 6l Claims. 1

This invention relates to electric heating .systems and: more especially to such systems applicable to the heating of electric. ovens., furnaces, and rooms in buildings:I altlfioughe itis use'- ful also wherever it is desired iso-supply by' con vection, forced or naturali, a current of heated air.

It has been proposed to heat ovens, furnaces, and ues by electric heater convection units formed of open coils of high resistance meta-1s disposed transversely of air passageways; but experience has shown that hea-t cana ybefr-nora uni formly imparted to a gasv atmosphere current and with less loss of gas velocity or pressure drop and with lower temperature gradient., by wiping action of the said current-over relatively wide heater elements curvilinear cross: section and disposed so as to change the course-of. the gas current.

The object of this invention is the provision: et an efficient and `economical electric gas. .atmos phere heating and turning lunit comprising an electrically heatable unit of high resistance metal formed to make a plurality ofspaced arcuate vanes disposed at the juncture or two.' angularlivl related ducts, conduits, ues or passageways and. substantially coextensive in .area withv that et the junction or atthe end ot suchpassageway .and substantially coextensive with the area. thereof, whereby to heat a gas, such- .as air, and. establish a flow thereof by convection, forced or natural..

Other objects and. the means for accomplishing them will hereinafter appear in thedetailed description of the embodiments yof my invention which have given good results inpractice..

In the drawings which accompany andv form a part of this speCiiicatiOn,

Figure 1 is a front elevation .of an electricr gas atmosphere heating and turning uni-t embody ing my invention.

Fig. 2 is a transverse section takenl on the line 2-2 of Fig. 1.

Fig. 3` is a horizontal section taken on the line 3-3 of Fig. 4 and illustrating. :a portion of an electric oven.

Fig. 4 is a vertical section taken onA the line 4-4 of Fig. 3.

Fig. 5 is a horizontal section takenon timeline 5-5 of Fig. 6, andy illustrating a portion ot anelectric furnace` l suitable means.

Fig. 6k is 4a' vertical sectionv taken on the line 6-6 of Fig. 5.

Fig. '7 is a horizontal .section 'of atypical elec'- tric oven.

Figure 8 is an edge view of a high resistance metallic strip before it is bent upon itself re'- peatedly to form a plurality of curvilinear spaced vanes.

Figures 9 and 10 are sectional views taken yon the lines 9-9 and Ill-Ill, respectively, of Fig. 8.

In the particular drawings selected .for more fully illustrating thel principle underlying. my invention and which are to be-considered as. illusitrative, merely, and not restrictive, III represents a unit made by repeatedly reversely bending upon itself a strip of any suitable'high: resistance metal that is curvilinear, for example,V arcuate incross section. They strip maybe given its sectional configuration `by dies or byA any other By bending said ystrip in the manner stated, there are produced a plurality of spaced varies I'I, I I', which deiine preferably, a1'- cuate passageway/s I2; that is to say, each vane defines with the vane next adjacent thereto.. a curvilinear or arcuatel passageway.y In theI form shown in Fig. 1, the end Vanes terminate .in ilat strips I3 adapted to connect the unit to a 4source of electric power for current ilow therethrough. It will be understood, however,v that vthe unit may not be a singleA unitary member as shown in Fig. L 'and that any suitable means may be ern'- ployedf for mechanically and electrically `connecting the Vanesr together ior` current ilowA therethrough and that the Vanes may beconnected in series with each other and with: the source! as illustrated, or 'so connected that they are in parallel with said source.

The heating and turning unit above described maybeused in many ways, two of which are illus'- trated in ther drawings.

In Figs.. 3" and 4, IlI- represents the walls. ot two ducts I 5., I6, that are angularly related, said: ducts being shown inthe present instance at right angles to each other. Thev unit is suitably sem curedat the'juncture of the ducts or passageways andas shown is .coextensive with thearea of said juncture.

In the particular form illustrated in Fig. the means for securing the unit in the ducts at the iuncture thereof and at an .angle te their respective axes, are strips of heat resisting insulation Il such as, for example, fused alumina insulation, which strips may be disposed in depressions I8 in the walls of the ducts, the surfaces of said strips contacting the ends of the unit being corrugated, as shown more clearly in Fig. 6, and indicated thereon by the numeral A suitable fan 20 may be employed to create a forced convection current of heated air or other gas, the flow of which is indicated by arrows. It will be noted that the forward end Zi of each Vane and therefore the passageway between a vane and the one next adjacent thereto is substantially parallel with the axis of the duct it from which the gas current is received and that the trailing end of each vane and passageway 22 is parallel with the axis of the duct lf3 to which the gas current is delivered.

In Figs. and 6, the application of my gas heating and turning unit to an electric furnace is shown, the distinction between an electric oven and an electric furnace being substantially that the temperature of the latter is usually in excess of 1000 F. and that of the forrner, usually below 1000 F. In Figs. 5 and E, the uncorrugated surfaces of the insulation members al. i' the plane inner walls of the duct, although it t, ll be understood, of course, that said walls be provided with the pockets lil shown The operation of the unit in a furnace is Fig. 3.

For producing a current of heated gas by natural convection the unit will be disposed in one of the lower corners of the oven or fu ace.

The unit may also be used to produce h ated air current in the iiues of buildings with or without one of the usual sources of heat. such source is used, the function of the unit will be to augment the heat delivered to rooms in the upper stories of the building.

In Fig. 7, 23 represents the walls of a typical electric oven in which the right-hand wall and the partition 2li defines a vertical duct i253 and the adjacent wall 25 and the partition iii define a duct 28 at right angles to the duct Disposed in the duct 2S immediately above an opening 29 in the partition 2l is a fan The heating and turning unit l ii is secured by insulation means such as above described at the ju c ture of the ducts 25, 28, and at an angle to the axes thereof, said unit being substantially coextensive with the area of said juncture. In the work area 3| of the oven will be disposed the usual shelves, trays, drawers, etc., for holding the articles to be treated. Any of the usual control systems may be employed, such as indicated by the thermocouple 32 and current controller If the heating unit is made in the manner shown in Fig. 1, by reversely bending repeatedly upon itself a strip of high resistance metal arcuate in cross section and the sectional configuration is imparted to the strip by dies, said strip will be died in the manner shown in Fig. S, which alternately spaced vanes are convex upwardly, as shown at l l, and convex downwardly, as shown at I l', each pair of vanes being connected by a short length of the flat strip l l, which when the strip is reversely bent, forms one of the ends of a pair of juxtaposed vanes, as indicated at Fig. 1, the portions Il constituting a means mechanically and electrically connecting the vanes together for current iiow therethrough.

Having thus described illustrative embodiments of my invention without, however, limiting the same thereto, what I claim and desire to secure by Letters Patent is:

1. An electric heating system comprising .in combination, a structure having two angularly related ducts, an electrically heatable unit located at the juncture of said ducts, said unit comprising a strip of high resistance metal curvilinear in cross section and reversely bent repeatedly7 upon itself to form a plurality of curvilinear spaced vanes defining passages therebetween, the forward end of each said vane being substantially parallel to the axis of one of said ducts and the trailing end of each said vane being substantially parallel to the axis of the other of said ducts, insulation means for securing said unit in said ducts at the juncture thereof and at an angle to the axes of said ducts, said unit being coextensive with the area of said juncture, and means adapted to connect said unit to a source of electric power.

2. An electric heating system comprising in combination, a plurality of spaced transversely arcuate vanes of high resistance material, means mechanically and electrically connecting vanes together for current flow therethrough, a structure defining two angularly related ducts, the forward end of each said Vane being substantially parallel to the axis of one of said ducts and the trailing end of the other of said vanes being substantially parallel to the axis of thc other of said ducts, insulation means securingr said vanes to said structure across the juncture of said ducts and means adapted to connect vanes with a source of electric power, where' y the air-flow from one of said ducts to the other will be through the passages defined by each adjacent pair of said vanes.

3. In an electric heating system, an electrically heatable unit comprising a strip of high resistance metal having curvilinear portions alternately convexed in opposite directions, said strip being reversely bent repeatedly upon itself to form a plurality of curvilinear spaced s defining curvilinear passages therebetween, whereby when said unit is electrically heated, will flow by convection through said passages.

4. In an electric heating system, a plur spaced transversely curvilinear vanes of ugh sistance material and means mechanically electrically connecting said vanes together for current iiow therethrough, each of said vanes defining with the vane next adjacent thereto, a transversely curvilinear passage, the walls of which are curvilinear in substantially the same general direction.

5. In an electric heating system, a set of spaced transversely curvilinear vanes of high resistance material, said vanes being transversely cui-vec. in substantially the same general direction, means mechanically and electrically connecting,r vanes in series with each other, and means adapted to connect said set of vanes with a source of electric power, whereby when said unit is electrically heated, air will flow by convection through the passages 4between each pair of said vanes.

6. An electric heating system comprising in combination, a structure having two angularly related ducts, an electrically heated unit locat at the juncture of said ducts, said unit comp ing a strip of high resistance metal having curvilinear portions alternately convexed in opposite directions, said strip being reversely bent repeatedly upon itself to form a plurality of transversely 5 6 curvilinear spaced vanes defining air passages REFERENCES CITED therebetween, insulation means for securing said i unit in said ducts at the juncture thereof and at lglef ilgwlaltgertferenls are of record m the an angle to the axes of said passageways, said unit y p being coextensive with the area of said juncture, 5 UNITED STATES PATENTS and means adapted to connect said unit to a source of electric power whereby when said unit Nlilell Kelile Jul Dzagtelgzg is electrically heated, air will now through said 1,829765 Spaldn Nosr 3, 1931 passages by Convection from one of said duets to 1,831151 Walker g --NOV .10, 1931 the other. m i

WALTER G. GRABEAU. 1,923,142 Trent et a1 sept. 26, 1933 2,221,703 Falco NOV. 12, 1940 

